2012 R2 Web Application Proxy - Block Some Users

We have ADFS running on 2012 R2. We also have Web App Proxy on 2012 R2 in front of ADFS. We currently only use this with Office 365.

I have a need to block some users from Office 365 when they are external to the office. Can I do this with Web App Proxy? It would appear to be the best place to block users from accessing O365 when external.

Thanks,

Paul